1. Field of the Invention
This invention relates to a cutting tool for a stump cutter device, having a holder and at least one cutter insert unit, wherein the cutter insert unit has a cutter head and a shank, and the cutter insert unit can be connected with the holder by its shank. This invention also relates to a cutter insert unit, having a cutter head, a shank and a cutter insert, wherein the shank is arranged at an angle with respect to the cutter head, and the cutter head has a front cutting edge which is formed at least partially by a cutter insert of a mechanically resistant material.
2. Discussion of Related Art
A known cutting tool and such a cutter insert are taught by German Patent Reference DE 690 21 215 and U.S. Pat. No. 5,497,815.
Such cutting tools are used in tree stump cutting devices that have a vertical disk, which can be rotated by a motor and on which cutting tools are mounted. To remove a tree stump, the rotary disk is rotated and is lowered onto the tree stump. A portion of the stump is removed by lateral pivoting. If required, the rotary disk can also be moved in the direction toward the operator and away from the operator. If one level is removed, the rotary disk is lowered. This process is repeated until the desired area is removed.
The cutting tools are vertically mounted on the lateral faces of the rotary disk in pairs, are located opposite each other and are distributed over the circumference of the rotary disk. The cutting tools are fastened on the rotary disk by fastening elements, such as bolts or screws. The cutting tools have holes for this purpose, through which the fastening elements are guided. The holes are shaped so that the fastening elements can be mounted through them without projecting toward the outside, so that movement of the cutting tool is not impeded during operation.
Cutting tools are mounted on the circumference of the rotary disk at various angles with respect to the contact face, to obtain a wider removal area. Straight cutting tools, as well as those angled toward the left and right, are used for this purpose.
The cutting tool contains a work head equipped with a cutter insert of a mechanically resistant material which is intended to insure a sufficient service life of the cutting tool. However, damage can occur from nails around which the tree stump has grown, or from stones. The cutting tools must be easily exchangeable because of this damage and of the wear occurring during the operation.
The work head is streamlined so that it can glide over the contact face between the work head and the stump surface with little effort.
Cutting tools are known from German Patent Reference DE 690 21 215, wherein a shank is connected to the work head. The shank engages a correspondingly shaped slit in a holder, which contains holes for mounting. The correct position of the shank on the holder is achieved by a peg on the holder and a peg retaining recess in the shank. The cutting tool is fastened on the rotary disk by bolts, together with a laterally reversed cutting tool. One disadvantage of this device is the complicated structure of the holder because of the peg, and in an elaborate assembly of the parts. Furthermore, the forces occurring during the operation act on comparably small surfaces of the shank and the holder, which results in increased wear.
One-piece cutting tools are known from U.S. Pat. No. 5,497,815 in which the holder, shank and work head with a cutter plate are combined into one part. It is disadvantageous with this device for the cutting tools, which are angled with respect to the contact face, to have a complicated shape and are therefore elaborate to produce. Also, in case of damage, the entire part must be replaced each time.